Plural stage rotary drum pulverizers, with grinding plates of regular polygonal shape



D. DEMAREST 2,730,307 PLURAL STAGE ROTARY DRUM PULVERIZERS, WITH GRINDING PLATES OF REGULAR POLYGONAL SHAPE Filed NOV. 21, 1952 2 Sheets-Sheet 1 Jan. 10, 1956 Jan. W, 1956 D. D. DEMAREST PLURAL STAGE ROTARY DRUM PULVERIZERS, WITH GRINDING PLATES OF REGULAR POLYGONAL SHAPE Filed Nov. 21., 1952 2 Sheets-Sheet 2 INVENTOR.

United States Patent PLURAL STAGE RUTARY DRUM PULVERIZERS,

WITH GRINDING PLATES OF REGULAR POLYC- ONAL SHAPE Daniel Douglas Demarest, Port Washington, N. Y.

Application November 21, 1952, Serial No. 321,833

8 Claims. (Cl. 241-153) This invention relates to grinding mills of the kind in which material to be ground is fed into an inclined rotary drum and is there subjected to the grinding action of bodies which are caused to turn relative to the drum in response to the rotation of the drum turns.

It is a primary object of the invention to provide a more effective grinding action while reducing the friction, and thereby reducing the expenditure of power.

To this end it is an important feature of the invention that the grinding elements are made to comprise polygonal plates having rounded or filleted corners, the plates being supported upright and being designed to effect the crushing and grinding of the work material in cooperation with the inner surface of the drum through a combined hammering, rolling and sliding action.

It is a further feature that spacers are provided to divide the grinding plates into groups, thereby to reduce friction and to level off any fluctuations in the rate of flow of coal to the mill. It is an important point that the grinding plates are not crowded together by the spacers, but are loosely confined between spacers with freedom for relative movement. This avoids unnecessary friction and leaves each plate individually free to fulcrum on one of its rounded corners and flap over as soon as it reaches a condition of instability.

It is a still further feature that stationary scrapers are provided for preventing the carrying around of the material by centrifugal force.

Yet another feature has to do with the provision of a bar which is passed axially of the drum through holes in the plates, and which assists in supporting the spacers and scrapers.

Other objects and advantages will hereinafter appear.

In the drawing forming part of this specification:

Figure l is a fragmentary view in sectional side elevation of an illustrative drum mill embodying features of the invention;

Figure 2 is a transverse sectional view taken upon the line 2--2 of Figure 1, looking in the direction of the arrows;

Figure 3 is a transverse sectional view taken upon the line 33 of Figure 1, looking in the direction of the arrows;

Figure 4 is a view in end elevation illustrating the action of a single grinding plate;

Figure 5 is a view similar to Figure 1 showing another illustrative form of drum mill in which features of the invention are embodied;

Figure 6 is a transverse vertical sectional view taken upon the line 6-6 of Figure 5, looking in the direction of the arrows;

Figure 7 is a diagrammatic view illustrating the employment of triangular grinding plates in place of the square plates shown in the preceding figures; and

Figure 8 is a view similar to Figure 7, but illustrating the employment of pentagonal grinding plates.

While the illustrative grinding mills are of general utility, they have been especially contrived for the purpose of acting upon coal in the form of lumps substantially the size of rice grains, and reducing these lumps to a powder fine enough to float in the air like smoke. The apparatus will, therefore, be illustratively described with reference to that use.

In the embodiment of Figures 1 to 4, a drum 1 is provided with tires 2. The tires run upon roller bearings 3 which are rotatively mounted in separate, fixed bearing blocks 4. A gear 5, affixed to the drum, is driven from a suitable source of power through suitable gearing (not shown) to turn the drum.

The drum comprises a flanged sleeve 6. A closure plate 7 is attached to the sleeve at the left hand or introductory end of the sleeve 6. The plate 7 has a central opening through which granulated coal is introduced into the drum. The coal is desirably blown into and out of the drum by an air blast which may be either forced or induced. With a forced draft the entire unit is maintained under pressure; with an induced blast the entire unit is maintained under suction. Since the employment of both forced and induced blasts is conventional, the mechanism for producing the blast is not illustrated.

The granulated coal is supplied from a hopper 8 through a conduit 9, which conduit extends into the central opening of the plate 7. A sealing and supporting plate 10 surrounds the delivery end of the conduit 9 in sealed engagement with it, and is pressed against the closure plate 7. A sealing gasket 11, lodged in an annular recess of the sealing plate 10, is pressed by the plate into sealing engagement with the outer face of the closure plate 7. A slide plate or valve 12 is provided for controlling the feeding of the coal from the hopper to the conduit 9. A spacer plate 13 extends across the entrance to the drum, being supported at a short distance inward from the plate 7 by legs 14. The plate assures a free passageway for the coal as it flows into the drum.

An elevator shell 15 is secured to the flange at the right hand end of the sleeve 6. This shell is of larger diameter than the sleeve 6 and is concentric with the sleeve 6 so that it extends outward uniformly beyond the periphery of the sleeve. Thus the coal which passes beyond the right hand end of the sleeve 6 drops into the bottom of the shell 15. The shell is equipped with elevator scoops or vanes 16, which cause the coal received in the bottom of the shell to be carried up and around as the shell turns with the sleeve 6, and to be dumped onto an inclined extension plate 17 of an inclined chute 18. While the chute 18 is inclined, it is unitary with a vertically disposed supporting and closure plate 19. The plate 19 includes a circular boss 20 in coaxial relation with the sleeve 6 and the shell 15. The boss fits into a circular central opening 21 which is formed in the outer face of the shell .15. A gasket 22 is pressed by the plate 19 into sealing engagement with the outer face of the shell 15.

The important features of the invention are concerned with the parts mounted within the drum. As shown, groups of grinding plates 23 are confined to assigned longitudinal zones of the drum by the spacer plate 13 and by spacers 2 Each spacer 24 comprises a central block or hub 25 having radial arms or spokes 26 rigid with it. Each arm 26 has a reduced threaded outer end portion which is passed through the wall of the sleeve 6 and clamped to the sleeve Wall by a nut 27. The spacers divide the grinding plates into loosely associated groups, each plate being free to turn relative to its neighbors, and having substantial freedom for movement axially of the drum with reference to them. The freedom of the plates avoids friction between adjacent plates. The freedom of the plates is not, however, sufficient to expose any one of them to the liability of becoming turned on its side.

The grinding plates are, preferably, of such size as to occupy a substantial portion of the cross sectional area of the drum (see Figures 6, 7 and 8). They are also, preferably, of such height as to extend above the central portion of the drum and thus overlap in height the spacer elements (see Figs. 1 and The spacers are so constructed that they at least extend substantially from the periphery of the drum to a point past the center thereof (see Figures 1 and 5). In the modification of this invention shown in Figure 5, the spacers extend from one side of the drum past its center to a point short of the other side of the drum. In the modification shown in Figure 1, the spacers extend clear across the drum.

The action of one of the grinding plates is well illustrated in Figure 4, in which successive positions of a single plate 23 are designated 23a to 23a inclusive. In the position 23a the block has just fallen from substantially the position marked 230. Since the center of gravity of the heavy block falls a substantial distance and the impact of the blow is concentrated in the restricted area of the lower left hand rounded corner of the block, the resulting pounding action has a very substantial crushing effect. As the grinding plate is carried around through positions 23b, 23c and 23d, the pressure is concentrated in the lower right and left hand corners. There is a relative rolling action through this sector so that the desirable features of roller grinding come into play. As the lower left hand corner advances from the position marked 23c to the point at which the block will again fall over, there is a tendency for the block to slide backward relative to the sleeve 6, with practically the entire weight of the plate concentrated in the lower corner of the plate. Thus, the plate exerts first a hammer action, then a rolling action and finally a sliding action, all with a concentration of the plate weight in one or two corners at a time. Each of these actions contributes importantly to the pulverization of the coal, and the combination of the three produces a very effective and satisfactory result.

Because the grinding plates are not pressed together, there is relatively little friction involved in the present mill as compared with conventional grinding mills. As a consequence, the drum can be turned rapidly without undue strain. This results in a high rate of work production and/or an exceptionally thorough pulverization.

The mill of Figure 5 is generally like the mill of Figure 1 as to its external features. Corresponding reference numerals have accordingly been applied to corresponding parts with the subscript a added in each instance, and the description will be confined to those features which diffor from the showing of Figure 1.

The shell a of Figure 5 is a tapered end closure shell.

The conduit 9a extends into the left hand end of the drum a short distance and has rigidly affixed to it an arm 30 which extends upward to the top of the drum and downward across the axis of the drum. In the axial portion the arm 3!) is offset inwardly to provide a clear passage for the entering coal. At the opposite end of the drum a chute 17a is extended inward and has unitary with it a cruciform support and spacer 31. One portion of the spacer 31 extends to the top of the drum while another extends across the drum axis. Still other parts serve merely to limit the right hand movement of the right hand group of grinding plates 2311.

A non-circular rod 32, which is preferably square in cross section as shown, is rigidly supported by the arm 30 and the spacer 31. The rod 32 extends free through circular openings 33 formed centrally in all the grinding plates, the opening being made large enough so that the rod will not, under any circumstances, interfere with the intended action of the grinding plates as described'in connection with Figure 4. The rod 32 serves as a rigid, fixed support for mounting at intervals of non-rotary cruciform spacers 34. One of the spacers 34 is seen in outline in Figure 6. The spacer 31 is of the same form. As before, the spacers together with the spacer arm 30 divide the grinding plates into loosely associated groups and determine the axial limits of the zones of action of the respective groups.

The upper ends of the stationary spacers 31 and 34 and of the arm 30 serve as supports for a stationary rod 35. The rod 35, in turn, serves to support stationary scraper blades 36 which are fixedly secured to it. Each scraperblade 36 extends continuously from one of the rod supports to the next, so that in all zones continuous provision is made for dislodging from the wall of the sleeve 6 any coal that is carried by centrifugal force around into the upper part of the sleeve.

The drum 15a of Figure 5 is intended to be driven at higher speeds than the drum 15 of Figure 1. Accordingly, the drum 15a is equipped with a driving pulley 37 in place of the gear 5 of Figure 1. It is for that reason also that the elevator buckets or vanes may be dispensed with in Figure 5, and that the scrapers are provided.

In Figure 7 the structure is varied only in the fact that equilateral triangular grinding plates 23b having rounded corners are employed in place of the square grinding plates of Figures 1 to 6.

In Figure 8 the structure is again varied by substitution of regular pentagonal grinding plates 230 having rounded corners for the square grinding plates of Figures 1 to 6. The invention can be best practical with plates having not more than five sides.

The plates 23b and 230 are shown solid, but they may be formed with central openings like the openings 33 of the plates 23a when they are to be used in a mill like the one shown in Figure 5.

I have described what I believe to be the best embodiments of my invention. I do not Wish, however, to be confined to the embodiments shown, but what I desire to cover by Letters Patent is set forth in the appended claims.

I claim:

1. In a grinding mill, the combination with a rotary drum of a series of grinding plates supported edgewise in the drum, each grinding plate being substantially in the form of a regular polygon of not more than five sides, and having rounded corners, spacers within the drum which separate the grinding plates into loosely associated groups, and means supporting the spacers in fixed locations axially of the drum, each spacer including radial supporting arms through which it is connected to the drum for rotation in unison therewith and each grinding plate being of such size as to occupy a substantial portion of the cross sectional area of said rotary drum.

2. In a grinding mill, the combination with a rotary drum of a series of grinding plates having openings therein supported edgewise in the drum, said openings being of such character as to allow for rotary and grinding action of said grinding plates, each grinding plate being substantially in the form of a regular polygon of not more than five sides, and having rounded corners, spacers in the drum which separate the grinding plates into loosely associated groups, and means supporting the spacers in fixed locations axially of the drum, the spacer supporting means including a fixed supporting rod disposed axially of the drum and extending through the openings in all the grinding plates, the spacers being fixed against both axial and rotative movement on the rod and clearing the bottom of the drum by a substantial amount.

3. In a grinding mill, the combination with a rotary drum of a series of grinding plates having openings therein supported edgewise in the drum, said openings being of such character as to allow for rotary and grinding action of said grinding plates, each grinding plate being substantially in the form of a regular polygon of not more than five sides, and having rounded corners, spacers in the drum which separate the grinding plates into loosely associated groups, and means supporting the spacers in fixed locations axially of the drum, the spacer supporting means including a fixed supporting rod disposed axially of the drum and extending through the openings in all the grinding plates, the spacers being fixed against rotative movement on the rod, scrapers disposed in an upper portion of the drum for dislodging material carried around by centrifugal force, and scraper supporting means carried by the spacers.

4. In a grinding mill, the combination with a rotary drum of a series of grinding plates supported edgewise in the drum, each grinding plate being substantially in the form of a regular polygon of not more than five sides, and having rounded corners, spacers disposed at intervals along the drum for dividing the grinding plates into loosely associated groups, supporting means within the rotary drum supporting the spacers in fixed positions against axial or rotary movement, and scrapers supported from the spacers in the upper part of the drum for dislodging material carried around by centrifugal force.

5. In a grinding mill, the combination of a substantially circular rotary drum having inlet and outlet openings at opposite ends thereof, a series of grinding plates supported edgewise in the drum, a plurality of spacer elements within the drum extending substantially at least from the periphery past the center thereof, which separate said grinding plates into loosely associated groups, said grinding plates being substantially in the form of regular polygons of not more than five sides having filleted corners at the intersection of said sides, and being of 6 such size as to occupy a substantial portion of the cross sectional area of said rotary circular drum and extending above the central portion of said drum to thus overlap in height said spacer elements.

6. The combination according to claim 5 wherein the grinding plates are in the form of a square with filleted corners whose diagonal is greater than the radius of said rotary circular drum.

7. The combination according to claim 5 wherein the grinding plates are in the form of an equilateral triangle with filleted corners whose altitude is greater than the radius said rotary circular drum.

8. The combination according to claim 5 wherein the grinding plates are in the form of a regular pentagon with filleted corners Whose altitude is greater than the radius of said rotary circular drum.

References Cited in the file of this patent UNITED STATES PATENTS 52,532 Chubb Feb. 13, 1866 64,060 Bailey Apr. 23, 1867 422,581 Fairfield Mar. 4, 1890 2,501,166 Fraser Mar. 21, 1950 FOREIGN PATENTS 8,645 Austria Aug. 1, 1902 269,240 Italy Nov. 13. 1929 560,745 Germany Oct. 6, 1932 627,053 France May 28, 1927 750,404 France May 22,1933 

